So I just got an achievement for having been here for a year... except I've been here for five years.

I also got a 1 week GA medal. I don't know what to do?

File a ticket to have the medal removed (and your Loyalty Box awarded, if you didn't get your most recent one already), and post about it on the Achievement Bugs thread.

It's not a glitch. It's a new achievement. Since the first year achievement never awarded anything a new achievement was made and the prize is a 1 week GA.

But does it count if we've been a member for over a year?

From the achievement bug thread, someone put in a ticket and staff said its fine. No matter how long you've been here (as long as its more than a year) the medal is yours to keep since this is a new achievement released retroactively.

Oh, I never saw that, thanks for the info c:

Yup, Everyone gets one with a year+ account.